The background description provided herein is solely for the purpose of generally presenting the context of the illustrative embodiments of the disclosure. Aspects of the background description are neither expressly nor impliedly admitted as prior art against the claimed subject matter.
Subterranean oil and gas wells are formed by drilling a well bore through one or more subterranean formations which contain hydrocarbons that are to be extracted from the well. The well bore is typically drilled into the ground by operation of a drilling rig which is placed at the ground surface. A drill string fitted with a drill bit is assembled at the drilling rig and the drill bit is rotated and cuts the well bore into a soil, rock or other material or medium beneath the ground and through the hydrocarbon formation or formations. During or after drilling, a well casing may be installed in the well bore and is typically perforated at the location of each formation. A production string is inserted in the well bore to facilitate flow of the hydrocarbons under pressure from the hydrocarbon formation or formations, through the perforations and the production string to the surface of the well.
During the drilling operation, drilling fluid is typically pumped from the well surface through the drill string and is ejected from the drill bit at the cutting end of the string. The ejected drilling fluid then returns to the well surface through the annulus between the drill string and the well bore and is again pumped through the drill string, forming a continuous circulation loop. At the cutting end of the drill string, the pressurized and ejected drilling fluid strikes the medium, enhancing the cutting action of the drill bit and cooling and lubricating the bit. The lubricating effect of the drilling fluid also facilitates disengagement and removal or extraction of the drill bit from the medium and removal of the drill string from the well bore upon conclusion of the drilling operation.
A blowout preventer (BOP) is a large, specialized valve or similar mechanical device which is typically included in the drill string to release erratic pressures and uncontrolled flow of formation fluids from the well during drilling. Blowout preventers may also prevent tubing, downhole tools and drilling fluid from being blown out of the well bore when a blowout threatens. Therefore, blowout preventers are important to the safety of crew, rig and environment and to the monitoring and maintenance of well integrity. Blowout preventers are typically located at the mud line of the well bore, at a depth of 200-10.000 feet.
In well drilling operations, tests are periodically performed to corroborate the integrity of the BOP and verify that the BOP has the capacity to withstand the reservoir fluids and pressures in case of a surface blowout. In BOP testing, it may be required that the entire drill string be removed from the well bore and the BOP tested at the well surface, after which the drill string is reinserted in the well bore to resume drilling. The process of removing the drill string, testing the BOP and reinserting the drill string to resume drilling operations may take 2˜3 days, significantly interrupting the drilling operation and delaying ultimate production of hydrocarbons from the well.
Therefore, a subterranean drill string coupling and uncoupling method which expedites drilling operations interrupted by blowout preventer (BOP) testing is needed.